As with all mechanical air-exhausting devices, a clothes dryer, when operating, places a burden on the air handling, heating, and conditioning systems in a building. Already heated and conditioned air is lost to the atmosphere, and as a result, outdoor air needs to be admitted and conditioned to replace it. The common vent associated with a clothes dryer provides only a means whereby the exhaust air can escape to the atmosphere. What is needed is a means whereby "make-up" outdoor air is preheated and admitted into the building while the clothes dryer is operating.